SCITECH | AN INVASIVE SOLUTION: How can invasive plants be herbicidal?

Across fields and backyards lurks a beast in the shadows — a weed so invasive by nature that it conquers every patch of soil it touches. This so-called beast is Paragis.

According to recent studies by Ma et al., Eleusine indica, locally known as Paragis, causes 20–30% crop losses in crops such as cotton, rice, and others. Its competitive nature results in a significant reduction in agricultural yields.

Due to its use of the C4 photosynthetic pathway, Paragis is able to fix carbon dioxide (CO2) into a 4-carbon compound, oxaloacetate, within the mesophyll cells where photosynthesis occurs. This mechanism allows Paragis to thrive under high light intensity, heat, dry conditions, and limited water availability, enabling it to grow vigorously in open fields.

To address these problems, synthetic chemicals have been used to manage harmful weeds. For instance, dinitroaniline herbicides disrupt microtubule formation in plant cells. Without microtubules, cell division cannot occur, resulting in plant death.

However, Kaundun et al. show that grasses like Paragis develop resistance due to the repeated use of synthetic herbicides, resulting in mutations. A herbicide-resistant strain of Paragis, known as the “P106S mutation,” exhibits changes in the EPSPS gene, making it resistant to commonly used herbicides.

Additionally, synthetic herbicides such as dinitroaniline can pose health risks to humans. They contain endocrine-disrupting chemicals (EDCs) that interfere with the body’s hormone system and may increase the risk of cancer due to potential carcinogenic properties observed in some pesticides.

Due to these concerns, John Kerbee A. de Leon, a 16-year-old researcher from Rizal, Laguna, investigated the herbicidal activity of biochemical compounds in Caladium, a plant widely available in tropical regions.

According to Kerbee, Caladium contains bioactive compounds such as flavonoids, phenols, and polyphenols, which have demonstrated herbicidal effects on grasses and weeds.

“Yung caladium kasi is introduced siya na tumtubo sa tropical regions like sa Pilipinas kung saan locally sa amin maraming tanim dito—caladium kasi ay may mga bio-active compounds like flavonoids, phenols at polyphenols na nagpapakita sa ibang studies na may herbicidal effect sa Paragis” he said.

Using Caladium leaves, an ethanolic maceration extraction was performed to obtain a crude Caladium leaf ethanolic extract (CLEE). Treatments were prepared using concentrations ranging from 0% to 100% of the crude extract. The herbicidal properties were evaluated by observing leaf discoloration, wilting, and other symptoms indicative of plant death.

The results demonstrated that CLEE exhibits herbicidal activity, with leaf discoloration and other symptomatic changes observed in Paragis grass within one to two days. Among the concentrations tested, 50% and 75% CLEE showed the highest herbicidal activity, indicating that moderate concentrations of the extract can be lethal to Paragis grass.

However, observations on the sixth and seventh days indicated that the herbicidal effect of CLEE on Paragis plants was limited. Damage was primarily observed on the leaves, and complete plant death did not occur, suggesting that the plants were able to recover during this period.

This research demonstrates that not all invasive species are harmful; in fact, Caladium can suppress the invasive Paragis grass, indicating its potential as a natural weed control agent.

Across fields and backyards lurks a beast in the shadows — a weed so invasive by nature that it conquers every patch of soil it touches. This so-called beast is Paragis. But there is one invasive plant that can tame this beast: Caladium, making it an invasive solution.